Ten years ago I was deployed to Uzbekistan. Even then we knew that up to a third of the Uzbek population was in Russia either working or looking for work. But recent photos out of Moscow (not Tashkent, not Kazan or Baku) show enormous crowds of Muslim men and they are mostly Uzbeks with the square kufi caps.
Strangely, the Uzbeks I spoke to at our base near Karshi were secular & admired anything Russian, spoke Russian, & listened to Russian pop. One of them said, “Thirty years ago my Uzbek grandmother was wearing miniskirts, drinking vodka, & listening to the Rolling Stones”.
It’s the Chechens who are the main threat inside the Russian federation. Nobody speaks well of them & the Dagestanis seem to going terrorist as well.
But it is hard to say how much of this opinion was in itself a product of atheist indoctrination. The fact is that once the "king" was shown to have no clothes, religious consciousness poured in and in the case of Asia and North Caucuses it happened to be a radical Islamic militant religion. My impression is that the Uzbek in general are milder in temperament than some others: merchants not warriors.
The uncontrolled immigration to Russian big cities is not so much a terrorist problem but simply an irritating cultural presence; that creates tension on the every-day life level. for example, the Russians are not exactly appreciative of the custom to drop down in the middle of the street, block traffic and pray to Mecca, while sheep are being slaughtered in the side alleys. Certainly it slows down the schools where a Russian kid is now next to a kid who barely understands the language. The legal environment often sides with the immigrant because the immigrant is ethnic minority and so can do no wrong. Stuff like what we can easily imagine in America as well, where also there is no legal protection for natural-born citizens.